1. Field of the Invention
The present invention relates to a new and improved continuously adjustable diluting device for mixing predetermined volumes of liquid. These devices are commonly called pipettes and are widely used in medical laboratory work for intermixing precise volumes of a liquid sample and a diluting medium. U.S. Pat. No. 4,141,250 discloses a plural piston adjustable diluting device having a volume indicator assembly and the present invention is an improvement over that device in providing an exceptionally handy system for selectively determining a precise volume of liquid sample or diluent to be picked up when the diluting device is utilized.
2. Background of the Prior Art
The aforementioned U.S. Pat. No. 4,141,250 discloses a plural piston adjustable diluting device having a digital volume indicator assembly which provides a digitial readout for indicating the precise volume in milliliters of a sample of liquid to be drawn into the device and thereafter expelled after mixing with a predetermined volume of liquid diluent. Oftentimes diluting devices are handled by laboratory technicians wearing rubber gloves in order to avoid contamination and sometimes when carelessly manipulating the diluting device to a precisely selected volume, a portion of a thin rubber glove may become wedged or caught within a space formed between an internal adjustment knob and an adjacent wall surface of the body of the diluting device. Moreover, fine adjustment of a volume to a precise level as indicated by digital readout is sometimes difficult to obtain with gloves on because of the limited access or area available for turning an internally positioned volume adjustment member. Moreover, because of frictional engagement between the knob and surrounding wall surface, a relatively large amount of finger strength is required to make a volume adjustment.